1. Field of the Invention
The present invention relates to a convergence adjusting method needed where a plurality of projection display units, which project respective images onto a projection screen, are used to overlap the projected images on the projection screen to provide a single projected image at a higher level of brightness. This invention further relates to signal generating apparatus and projection display units.
2. Description of the Prior Art
A method for the providing of a large-scale screen image has been well known in the art, in which an optical image according to a video signal is formed on a light valve. Thereafter, the optical image thus formed is illuminated with light to be projected enlargedly onto a large-scale projection screen by a projection lens. In recent years, projection display units using liquid-crystal panels as light valves have attracted considerable attention. For example, Ono and others disclose a liquid-crystal projection display unit (Japanese Patent Laid-Open No. S62-133424), to provide a projected image of high quality by employing three active matrix liquid-crystal panels for three kinds of colors (red , green, and blue), each pixel thereof being provided with a TFT acting as a switching element. As a liquid-crystal panel material, twisted nematic (TN) liquid-crystal has been used widely owing to its ability to provide images of high quality. Because of improvements of an aperture ratio in the liquid-crystal panel and because of the development of small-sized lamps of high luminance, a typical latest projection display unit is able to provide much improved optical output than previously.
Additionally, a method for use by a display unit installed at an exhibition hall or the like has been known, in which projected images are overlapped or superposed on one another on a projection screen using a plurality of projection display units, for providing a single projected image at a much higher level of brightness. Hereinafter, such a method will be called the xe2x80x9cstack projectionxe2x80x9d technique. For instance, Noda proposes a technique for performing a stack projection operation with a plurality of liquid-crystal projection display units (Japanese Patent Laid-Open No. H05-107639). In addition, stack projection is employed where images which are thrown for right and left human eyes are projected using two projection display units for achieving a large-scale screen stereoscopic display.
However, in the case a plurality of projection display units are used to carry out stack projection of images, it is required that some adjustment work be made at the job site such as an exhibition hall for overlapping a plurality of projected images on one another on the projection screen.
Accordingly, in a conventional projection-type displaying technique, two projection display units are fed the same video signal to project identical crosshatch patterns onto a projection screen, wherein inter-set convergence adjustment is carried out by moving a projection display unit by a very slight amount or by moving a projection lens by a very slight amount, to reduce a degree of misregistration between the two crosshatch patterns over the entire projection screen.
Conventionally, convergence adjustment has been carried out in the following two ways.
In the first convergence adjusting method, one projection display unit displays a red crosshatch pattern and the other projection display unit displays a green crosshatch pattern, wherein inter-set convergence adjustment is performed to reduce a degree of misregistration between the red crosshatch pattern and the green crosshatch pattern. Next, the two projection display units display respective crosshatch patterns of white lines to confirm a resulting convergence state. If the convergence state thus confirmed is found to be unsatisfactory, another inter-set convergence adjustment operation is performed by redisplaying a red and a green crosshatch pattern. These operations are repeatedly performed until the point the misregistration between the crosshatch patterns displayed on the projection screen cannot be reduced to a further degree.
In the second convergence adjusting method, inter-set convergence adjustment is roughly performed using a red and a green crosshatch pattern. This is followed by the displaying of crosshatch patterns of white lines by the two projection display units. Performing adjustment with the aid of the displayed white-line crosshatch patterns, a final fine convergence adjustment process is carried out.
In each of the first and second convergence adjusting methods, crosshatch patterns of white lines are displayed to confirm a convergence state for the following reason. If crosshatch patterns of red, green, and blue, each projected from a single projection display unit, are precisely superposed upon one another, the projecting of any one of red, green, and blue crosshatch patterns may be considered equivalent to the projecting of a white-line crosshatch pattern. However, practically, there is produced slight misconvergence between projected red, green, and blue images due to the system assembly error and the magnification chromatic aberration. To cope with such misconvergence, it is necessary that the adjustment previously described is performed.
The first convergence adjusting method enables the operator to easily determine, based on the difference in line color between projected crosshatch patterns, which part of which projection display unit should be adjusted. However, the first convergence adjusting method is troublesome to carry out and such adjustment is very time consuming.
On the other hand, in the second convergence adjusting method, the two projection display units each display a crosshatch pattern of white lines in the fine adjustment phase, which makes it possible to detect misregistration between the crosshatch patterns. However, the problem of the second convergence adjusting method is that it is impossible to determine which part of which projection display unit should be adjusted. This may lead to another problem that a portion required to be adjusted is moved opposite. Such misadjustment may result in producing a poor inter-set convergence adjustment result in comparison with the adjustment result prior to the final fine adjustment. If such an undesired situation takes place, it takes quite a long time to perform necessary adjustment operations.
As described above, conventional inter-set convergence adjusting operations are very troublesome to perform and time consuming. This problem becomes more and more serious as the number of projection display units increases.
There is another type of projection display unit, namely a CRT projection display unit employing a CRT in which an image displayed on the CRT is enlargedly projected with a projection lens. Even when using a plurality of CRT projection display units to perform a stack projection operation, the same problem as above arises, in other words inter-set convergence adjustment becomes considerably troublesome to perform.
Bearing in mind the above-described problems with the prior art projection display units, the present invention was made. Accordingly, an object of the present invention is to provide an improved convergence adjusting method capable of facilitating convergence adjustment in a stack projection operation.
It is another object of the present invention to provide a projection display unit and a signal generating apparatus for facilitating, based on the convergence adjusting method of the present invention, convergence adjustment work in a stack projection operation.
The present invention is a convergence adjusting method which is employed where a plurality of projection display units are used to project identical images for mutual superposition, said convergence adjusting method comprising the steps of:
(a) causing a first one of said plurality of projection display units that serves as a reference to continuously project a first pattern,
(b) causing a second one of said plurality of projection display units to alternately periodically project a pattern identical with said first pattern and a second pattern different from said first pattern,
(c) adjusting convergence between said two projection display units on the basis of a state of superposition between said patterns projected from said first and second projection display units, and
(d) carrying out, in the same way as above, adjustment in convergence between said reference projection display unit and each of the remaining projection display units.
The present invention is a signal generating apparatus comprising:
(a) a first output terminal for continuously providing video signals for a first pattern, and
(b) a second output terminal for providing video signals so that a pattern identical with said first pattern and a second pattern different from said first pattern are periodically repeated in an alternating manner.
The present invention is a projection display unit comprising:
(a) a display unit for forming an image according to a video signal,
(b) a projection lens for projecting said image formed on said projection display unit onto a projection screen, and
(c) a signal generating apparatus for providing a pattern for convergence adjustment by making use of said projection display unit and said projection lens,
wherein said signal generating apparatus selects, based on a selection command, between (1) a first video signal for continuously displaying a first pattern and (2) a second video signal for alternately periodically displaying a pattern identical with said first pattern and a second pattern different from said first pattern, for providing said convergence adjustment pattern.
The present invention is a convergence adjusting method which is employed where a plurality of projection display units are used to project identical images for mutual superposition, said convergence adjusting method comprising the steps of:
(a) causing first and second ones of said plurality of projection display units to project respective patterns identical in shape but different in line type, said first projection display unit serving as a reference,
(b) adjusting convergence between said projected images on the basis of a state of superposition between said patterns projected from said first and second projection display units, and
(c) carrying out, in the same way as above, adjustment in convergence between said reference projection display unit and each of the remaining projection display units by causing each of said remaining projection display units to project a pattern different in line type from said pattern projected from said reference projection display unit.
The present invention is a signal generating apparatus comprising:
(a) a first output terminal, and
(b) a second output terminal,
wherein said first and second output terminals provide video signals for displaying their respective patterns identical in shape but different in line type.
The present invention is a projection display unit comprising:
(a) a display unit for forming an image according to a video signal,
(b) a projection lens for projecting said image formed on said display unit onto a projection screen, and
(c) a signal generating apparatus for providing a pattern for convergence adjustment by making use of said display unit and said projection lens,
wherein said signal generating apparatus selectively projects, based on a selection command, a particular one of various crosshatch patterns of different line types.
The present invention is a convergence adjusting method which is employed where a plurality of projection display units are used to project identical images for mutual superposition; said convergence adjusting method comprising the steps of;
wherein patterns to be projected by said plurality of projection display units are identical in shape but different, when viewed in time, in projection time zone and/or in line type among said plurality of projection display units, and
wherein by making utilization of said difference, adjustment of convergence between projection display units is carried out.
In accordance with the convergence adjusting method, the signal generating apparatus, and the projection display unit of the present invention, when using a plurality of projection display units to execute a stack projection operation, it becomes easy for the operator to determine which crosshatch pattern displayed on the projection screen is projected from which projection display unit, thereby providing the effect that inter-set convergence adjustment can be performed in an easier way. Accordingly, it becomes possible to provide a large-size, brighter, highly-converged, high-quality projected image.
Other features and operation of the present invention will appear more fully from the following detailed description of embodiments with reference to the accompanying drawings.